1. Field of the Invention
This invention generally relates to a sealing cup adapted for use in vehicular devices and more particularly to improvements in a sealing cup to be mounted on any piston and cylinder for receiving the fluid pressure and for providing a fluid seal.
2. Description of the Prior Art
In vehicles, lots of devices have been employed for pressurizing the fluid in which a piston fitted within the cylinder and a cup mounted on the piston constitute a cylinder chamber to be pressurized by the relative movement of the piston and the cylinder. In the field of brake devices, too, various improvements have been made to sealing or piston cups (hereinafter simply referred to as brake cup) in order to increase the sealing effect from the view point of safety. As a result, the seal requirement of the brake cup has been satisfied.
Recently, a new requirement of vehicle drivers is to improved foot feeling upon depression of the brake pedal. That is to say, the brake device has to provide a brake pedal that may be smoothly depressed with little resistance and which will stop the vehicle with a small depression of the brake pedal.
More specifically, one of the major drawbacks of the conventional brake cup, although satisfactory as regards sealing, is the increased resistance to sliding due to shortage of the oil film formed between the slide surfaces. Therefore, a large foot force is necessary to pressurize the brake fluid, causing a poor pressurizing efficiency of brake fluid. In addition, stable movement of the piston in a conventional brake cup is effected due to stick-slip vibration resulting in unstable brake application.